ABSTRACT:The mechanisms by which organoselenium compounds inhibit tumor formation during the initiation phase of carcinogenesis have been explored in vitro and in well defined animal model. Various organoselenium compounds were found to have the ability to decrease lipids and phospholipids hydroperoxide levels, hydrogen peroxide, thereby destroying the propagation of free radicals; reactive oxygen and nitric oxide species mediating cellular damage. Organoselenium may inhibit oxidative stress to cells that produce toxicity and malignant transformation of cells leading to cancer. Organoselenium compounds have received wide attention as possible cancer chemopreventive agent.